This photo shows a head-on view of NASA's SR-71B, used for pilot proficiency and training, on the ramp at the Ames-Dryden Flight Research Facility (later, Dryden Flight Research Center), Edwards, California. NASA operated two of these unique aircraft, an SR-71A, for high-speed, high altitude research, and this SR- 71B pilot trainer for most of the decade of the 1990s. The ''B'' model is special because of its raised rear cockpit, which provided a second pilot position so a trainer and an experienced pilot could both see what was going on during flights. The SR-71 was designed and built by the Lockheed Skunk Works, now the Lockheed Martin Skunk Works. Studies have shown that less than 20 percent of the total thrust used to fly at Mach 3 is produced by the basic engine itself. The balance of the total thrust is produced by the unique design of the engine inlet and ''moveable spike'' system at the front of the engine nacelles, and by the ejector nozzles at the exhaust which burn air compressed in the engine bypass system. Data from the SR-71 high speed research program will be used to aid designers of future supersonic/hypersonic aircraft and propulsion systems, including a high speed civil transport.